Intervertebral spacer

ABSTRACT

An intervertebral spacer adapted for implanting between adjacent vertebral bodies of a human spine as a load-bearing replacement for a spinal disc. The spacing member may include an external, non-porous, concavo-convex contour with respect to one dimension of the spacing member. The spacing member may be constructed from a rigid, non-resilient load-bearing material that is incapable of elastic deformation. The spacing member may be inserted with the aid of a sheathed trocar device that is releasably attached to the spacer, to enable implantation and selective positioning of the spacer by the surgeon from the posterior side of the spine, without the need to retract the dural nerve or the posterior longitudinal ligament.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of co-pending U.S. patent application Ser. No. 11/205,284, filed Aug. 15, 2005, entitled “Intervertebral Spacer,” which is a continuation of U.S. patent application Ser. No. 11/081,824, filed Mar. 15, 2005, entitled “Intervertebral Spacer,” which is continuation-in-part of U.S. patent application Ser. No. 10/957,328, filed Oct. 1, 2004 entitled “Intervertebral Spacer,” which is a continuation of U.S. patent application Ser. No. 10/800,418, filed Mar. 12, 2004, entitled “Intervertebral Spacer,” which is a continuation of U.S. patent application Ser. No. 10/643,779, filed Aug. 18, 2003, entitled “Intervertebral Spacer,” which is a continuation of U.S. patent application Ser. No. 10/358,103, filed Feb. 3, 2003, entitled “Intervertebral Spacer,” which is a continuation of U.S. patent application Ser. No. 10/188,281, filed Jul. 1, 2002, entitled “Intervertebral Spacer,” which is a continuation of U.S. patent application Ser. No. 09/592,072, filed Jun. 12, 2000, now U.S. Pat. No. 6,579,318, entitled “Intervertebral Spacer,” which applications are hereby incorporated by reference herein in their entireties, including but not limited to those portions that specifically appear hereinafter, the incorporation by reference being made with the following exception: In the event that any portion of the above-referenced applications is inconsistent with this application, this application supercedes said above-referenced applications.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable.

BACKGROUND

1. The Field of the Invention.

The present disclosure relates generally to an intervertebral spacer, and more particularly, but not necessarily entirely, to a interbody spacing system for accomplishing enhanced intervertebral fusion between adjacent vertebral bodies of a human spine.

2. Description of Related Art.

The human spine is a complex, sophisticated mechanical system. The vertebrate spine operates as a structural member, providing structural support for the other body parts. A normal human spine is segmented with seven cervical, twelve thoracic and five lumbar segments. The lumbar portion of the spine resides on the sacrum, which is attached to the pelvis. The pelvis is supported by the hips and leg bones. The bony vertebral bodies of the spine are separated by intervertebral discs, which reside sandwiched between the vertebral bodies and operate as joints allowing known degrees of flexion, extension, lateral bending and axial rotation.

The intervertebral disc primarily serves as a mechanical cushion between adjacent vertebral bodies, and permits controlled motions within vertebral segments of the axial skeleton. The disc is a multi-element system, having three basic components: the nucleus pulposus (“nucleus”), the annulus fibrosus (“annulus”) and two vertebral end plates. The end plates are made of thin cartilage overlying a thin layer of hard, cortical bone that attaches to the spongy, richly vascular, cancellous bone of the vertebral body. The plates thereby operate to attach adjacent vertebrae to the disc. In other words, a transitional zone is created by the end plates between the malleable disc and the bony vertebrae.

The annulus of the disc forms the disc perimeter, and is a tough, outer fibrous ring that binds adjacent vertebrae together. The fiber layers of the annulus include fifteen to twenty overlapping plies, which are inserted into the superior and inferior vertebral bodies at roughly a 40 degree angle in both directions. This causes bi-directional torsional resistance, as about half of the angulated fibers will tighten when the vertebrae rotate in either direction.

It is common practice to remove a spinal disc in cases of spinal disc deterioration, disease or spinal injury. The discs sometimes become diseased or damaged such that the intervertebral separation is reduced. Such events cause the height of the disc nucleus to decrease, which in turn causes the annulus to buckle in areas where the laminated plies are loosely bonded. As the overlapping laminated plies of the annulus begin to buckle and separate, either circumferential or radial annular tears may occur. Such disruption to the natural intervertebral separation produces pain, which can be alleviated by removal of the disc and maintenance of the natural separation distance. In cases of chronic back pain resulting from a degenerated or herniated disc, removal of the disc becomes medically necessary.

In some cases, the damaged disc may be replaced with a disc prosthesis intended to duplicate the function of the natural spinal disc. U.S. Pat. No. 4,863,477 (granted Sep. 5, 1989 to Monson) discloses a resilient spinal disc prosthesis intended to replace the resiliency of a natural human spinal disc. U.S. Pat. No. 5,192,326 (granted Mar. 9, 1993 to Bao et al.) teaches a prosthetic nucleus for replacing just the nucleus portion of a human spinal disc.

In other cases it is desired to fuse the adjacent vertebrae together after removal of the disc, sometimes referred to as “intervertebral fusion” or “interbody fusion.”

In cases of intervertebral fusion, it is known to position a spacer centrally within the space where the spinal disc once resided, or to position multiple spacers within that space. Such practices are characterized by certain disadvantages, including a disruption in the natural curvature of the spine. For example, the vertebrae in the lower “lumbar” region of the spine reside in an arch referred to in the medical field as having a sagittal alignment. The sagittal alignment is compromised when adjacent vertebral bodies that were once angled toward each other on their posterior side become fused in a different, less angled orientation relative to one another.

Another disadvantage of known spacing techniques and intervertebral spacers are the additional surgical complications that arise in the use of multiple spacers in a single disc space. In such cases, surgeons will often first perform a posterior surgery to remove the affected disc and affix posterior instrumentation to the posterior side of the vertebrae to hold the posterior portions of the vertebrae in a desired position. Placement of the multiple spacers is often too difficult to accomplish from the posterior side of the patient, at least without causing with undue trauma to the patient, because a surgeon would need to retract the dura nerve as well as the anterior longitudinal ligament, thereby increasing damage, pain and morbidity to the patient. Surgeons have therefore often chosen to turn the patient over after completing the posterior surgical portion, to perform an anterior operative procedure, through the patient's belly, in order to insert multiple spacers between the vertebrae from the anterior side instead of from the posterior side.

U.S. Pat. No. 5,961,554 (granted Oct. 5, 1999 to Janson et al.) illustrates a spacer having a high degree of porosity throughout, for enhanced tissue ingrowth characteristics. This patent does not address the problem of compromising the sagittal alignment, or of increased pain and trauma to the patient by implantation of multiple spacers in a single disk space.

The prior art is thus characterized by several disadvantages that are addressed by the present disclosure. The present disclosure minimizes, and in some aspects eliminates, the above-mentioned failures, and other problems, by utilizing the methods and structural features described herein.

The features and advantages of the disclosure will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by the practice of the disclosure without undue experimentation. The features and advantages of the disclosure may be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the disclosure will become apparent from a consideration of the subsequent detailed description presented in connection with the accompanying drawings in which:

FIG. 1 is a perspective view of an intervertebral spacer, made in accordance with the principles of the present disclosure;

FIG. 2 is a plan view of the intervertebral spacer of FIG. 1;

FIG. 3 is a frontal view of the intervertebral spacer of FIGS. 1 and 2;

FIG. 4 is a side view of the intervertebral spacer of FIGS. 1, 2 and 3;

FIG. 5 is side view of a pair of adjacent vertebral bodies from the lumbar region of a human spine;

FIG. 6 is a schematic view of a sheathed trocar device releasably attached to a trial spacer shaped similarly to the intervertebral spacer of FIG. 1, in accordance with the principles of the present disclosure;

FIG. 7 is a schematic view of a sheathed trocar device releasably attached to the intervertebral spacer of FIG. 1, in accordance with the principles of the present disclosure;

FIGS. 8A-8D illustrate a schematic progression of the placement of the intervertebral spacer of FIG. 1 between vertebral bodies of a human spine;

FIG. 9 illustrates posterior instrumentation by which compression is applied to the posterior sides of a pair of adjacent vertebral bodies of a human spine;

FIG. 10 is a side view of an alternative embodiment intervertebral spacer;

FIG. 11 is a back view of an alternative embodiment intervertebral spacer; and

FIG. 12 is a cross-sectional view of the alternative embodiment intervertebral spacer of FIG. 11, taken along line A-A.

DETAILED DESCRIPTION

For the purposes of promoting an understanding of the principles in accordance with the disclosure, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the disclosure is thereby intended. Any alterations and further modifications of the inventive features illustrated herein, and any additional applications of the principles of the disclosure as illustrated herein, which would normally occur to one skilled in the relevant art and having possession of this disclosure, are to be considered within the scope of the disclosure claimed.

Before the apparatus and methods of the present disclosure are described further, it is to be understood that the disclosure is not limited to the particular configurations, process steps, and materials disclosed herein as such configurations, process steps, and materials may vary somewhat. It is also to be understood that the terminology employed herein is used for the purpose of describing particular embodiments of the disclosure only, and is not intended to be limiting since the scope of the present disclosure will be limited only by the appended claims and equivalents thereof.

The publications and other reference materials referred to herein to describe the background of the disclosure and to provide additional detail regarding its practice are hereby incorporated by reference. The references discussed herein are provided solely for their disclosure prior to the filing date of the present application. Nothing herein is to be construed as a suggestion or admission that the inventors are not entitled to antedate such disclosure by virtue of prior invention.

In describing and claiming the present disclosure, the following terminology will be used in accordance with the definitions set out below.

As used herein, “comprising,” “including,” “containing,” “characterized by,” and grammatical equivalents thereof are inclusive or open-ended terms that do not exclude additional, unrecited elements or method steps.

Applicants have discovered that several of the disadvantages of the prior art spinal disc replacement systems can be minimized, or even eliminated, by the use of a cashew-shaped interbody spacer having a tapered external shape, placing it is far anteriorly as possible between adjacent vertebral bodies, filling in the remaining posterior space with bone graft material, and applying compression to posterior portions of the vertebral bodies to load the bone graft in compression and restore sagittal alignment.

Referring now to FIGS. 1-4, there is shown a spacing member, referred to also herein as an intervertebral spacer or an interbody spacer, designated generally at 10.

Briefly stated, the spacer 10 may be utilized, along with autogenous bone grafting material, to replace a diseased or damaged spinal disc. Referring now to FIGS. 5-7, the procedure may be implemented by making an incision 32 in the annulus 34 connecting adjacent vertebral bodies 31. The spinal disc (not shown) may be surgically removed from the incision 32, after which the spacer 10 is placed through the incision 32 into position between the vertebral bodies 31. The spacer may be placed with its convex, anterior sidewall 12 facing anteriorly, and with its concave, posterior sidewall 14 facing posteriorly. Bone grafting material may be placed through the incision 32 to reside behind the spacer 10, after which posterior instrumentation may be attached to pedicle areas 34 to force the vertebral bodies 31 together in compression, as illustrated schematically in FIG. 8D and more particularly in FIG. 9.

The unique aspects and procedures relating to the spacer 10 will now be explained in more detail. Some of the key features of the disclosure comprise the size, shape and placement of spacer 10. The spacer 10 may be made of titanium, thus having a non-porous quality with a smooth finish. The spacer 10 could also be made of ceramic, stainless steel or other metallic materials, nitinol, nylon, polyethylene, polyetheretherketone (PEEK), polyurethane, polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE) or any suitable polymer, carbon, hydroxyapatile or any other suitable material that is inert or biologically compatible, such as bone including, but not limited to, allogenic or xenogenic bone implants. The term “non-porous” as used herein shall be construed broadly in accordance with the common, ordinary meaning of that term to refer to objects possessing an impediment to flow that would operate in the presence of fluid to impede or even block fluid flow through the object. In accordance with such common, ordinary meaning, such objects are either impermeable by liquid, or possess a limited degree of permeability that prevents liquid from passing through the object in a manner that would be considered flow. Examples of objects that are non-porous and impermeable include a solid titanium or solid ceramic intervertebral spacer, or a spacer made from impermeable bone material, or a spacer that is coated or treated in some way to render it impermeable. Examples of objects that are non-porous and possess a limited degree of permeability, and which therefore do not permit fluid to pass through them in a flowable manner, include biologically compatible spacers made from bone, such as milled-bone allograft spacers or particle-bone allograft spacers that are freeze-dried and thereafter re-hydrated prior to insertion, or any other type of non-porous spacer made from bone. Under the definition above, the presence or absence of surface porosity on an object, such as an intervertebral spacer, is irrelevant to whether the object is porous or non-porous. The spacer 10 may be thus constructed from a rigid, non-resilient load-bearing material, one that may be incapable of elastic deformation. The spacer 10, by its anterior, convex sidewall 12 and its posterior, concave sidewall 14, has thereby a concavo-convex contour with respect to one dimension.

The phrase “solid body” as used herein shall refer to the concept of the spacer 10 having no through holes, nor any internal encapsulated voids other than naturally occurring voids existing in the material used to construct the spacer 10. The phrase “through hole” as used herein shall refer to a hole formed in and extending through a body and having an entrance and an opposing exit, in a manner such that any line, including but not limited to straight, curved, or tortuous lines, may extend continuously from said entrance through some portion of the hole along any path to reach the exit.

It is to be understood that the concept of an object having a concavo-convex contour with respect to one dimension of the object, as referred to herein, shall not require the concave and convex sides of the object to be parallel to one another, although such may be preferred. The concept does however refer to a dimension in which the concave and convex sides of the object are at least partially facing the direction of that dimension, as indicated by the dimension 16 of FIG. 1 in relation to the spacer 10. It is also to be understood that the concept of an object being concavo-convex in a single dimension shall thereby include an object that has concave and convex sides 14 and 12 in a horizontal dimension 16, even though those very same sides are linear in a vertical dimension 20 at all points, such as in the case of the spacer 10 shown in FIG. 1. For example, the spacer 10 is concavo-convex in the anterior-posterior direction 16, though not in a medial-lateral direction 18 or vertical direction 20.

The upper surface 22 of the spacer 10 may be a planar, discontinuous surface as shown, having a plurality of spaced-apart elongate recesses 24, with a corner point 28 whereby one side 26 or portion of the spacer 10 begins tapering in the medial-lateral direction 18, as shown most clearly in FIG. 3. The tapered side 26 may facilitate insertion of the spacer 10 and may be sized to extend along a portion of a length L such that the tapered side 26 covers less than approximately 25% of the length L. By tapering less than 25% of the length L of the spacer 10 in a medial-lateral direction, the upper surface 22 and lower surface 30 may support the spinal disc without causing a lateral curvature or scoliosis. The tapered side 26 may begin at a male corner line 28 a, which starts at the corner point 28. It will be appreciated that the orientation of the male corner line 28 a may vary such that the tapered side 26 may have various different configurations within the scope of the present disclosure. It will also be understood that in an alternative implementation of the present disclosure, the tapered side 26 may be formed as a curved surface without the presence of the corner point 28. Accordingly, the tapered side 26 may be configured to gradually blend into the upper surface 22 or the lower surface 30 without a male corner line 28 a.

Accordingly, the spacing member or spacer 10 may be configured such that the upper surface 22 and the lower surface 30 may terminate in a free insertion end at R₄ in FIG. 2. At least one of the upper surface 22 and the lower surface 30 may include the male corner line 28 a. The spacer 10 may include a tapered portion or side 26 between the male corner line 28 a and the free insertion end such that the spacer 10 becomes progressively thinner from the male corner line 28 a toward the free insertion end. The tapered portion 26 may be characterized by at least one smooth surface that is a part of either the upper surface 22 or the lower surface 30 and extends from the male corner line 28 a to the free insertion end, the smooth surface having an absence of corners, points or other abrupt edges.

Further taper of the spacer 10 may occur in the anterior-to-posterior direction 16, in that the spacer 10 may narrow in thickness in a continuous manner along substantially the entire width of the spacer 10 as shown most clearly in FIG. 4. The upper surface 22 and lower surface 30 may form an acute angle relative to a horizontal plane 23, the angle may be within a range of approximately two to eight degrees, such as four degrees, for example. The entire taper may therefore be an eight degree total taper, with four degrees of taper resulting from the upper surface 22 and the other four degrees of taper resulting from the lower surface 30.

As shown most clearly in FIG. 2, the spacer 10 may have an arc-length AL that may be 1.218 inches, a width W that may be 0.320 inches, a depth D that may be 0.532 inches, an inner radius R₂ that may be 0.271 inches, an outer radius R₁ that may be 0.591 inches, and side radii R₃ and R₄ that each may be 0.160 inches.

The anterior, convex sidewall 12 and the posterior, concave sidewall 14 of the spacer 10 each may be linear in the vertical dimension 20, and may be parallel relative to one another. Moreover, in one implementation of the present disclosure, the convex sidewall 12 and concave sidewall 14 may form part of a perimeter of the spacer 10, such that the perimeter may have a smooth contour characterized by an absence of corners or abrupt edges as shown in the plan view of FIG. 2. It will be understood that the spacer 10 may include attachment means for releasably attaching positioning means to the spacer 10, such as the opening 10a or other such recesses, and still maintain the smooth contour to facilitate insertion of the spacer 10.

The spacer 10 may be also constructed from bone, such as allogenic bone or allograft material. The allogenic spacer 10 may be machined from human bone, but could also comprise xenogenic bone or xenograft material as known to those skilled in the art. The spacer 10 could also comprise reconstituted pulverized bone in a manner known to those skilled in the art.

In other embodiments of the spacer 10, such as those involving allogenic bone, the spacer 10 may have substantially the same shape and size as the spacer 10 described in the previous embodiment. However, the upper and lower surfaces, 22 and 30 respectively, of the spacer 10 may also be either planar or curved. The upper and lower surfaces 22 and 30 may be configured without any recesses 24. Moreover, the spacer 10 may have multiple rows of teeth (not shown) projecting from the upper and lower surfaces, 22 and 30 respectively.

In addition, as shown most clearly in FIG. 10, an alternative embodiment spacer 11 may have an upper surface 22 a and a lower surface 30 a that may be oriented at substantial right angles to the sidewalls 12 a and 14 a. Thus, the surfaces 22 a and 30 a may not taper in an anterior-posterior direction. Accordingly, the upper surface 22 a and the lower surface 30 a may be substantially parallel to a horizontal plane 23 a. It will be understood that other implementations of the present disclosure may include a spacer with sidewalls that are not oriented at right angles with the upper surface 22 a and the lower surface 30 a, but in which the upper surface 22 a may still be substantially parallel to the lower surface 30 a. Moreover, the upper surface 22 a and the lower surface 30 a may be somewhat dome shaped.

In one implementation of the present disclosure, the alternative embodiment spacer 11 may be formed with recesses 24 a having sidewalls 27 and bottom portions 29. As best shown in FIG. 11, opposing sidewalls 27 in the recesses 24 a may be configured to form a non-parallel angle α with respect to each other. The angle α may be formed at various different angles, such as angles within a range of between approximately 45 to 75 degrees, for example. One implementation of the present disclosure includes sidewalls 27 at an angle α of approximately 60 degrees, for example. This configuration may allow the spacer 10 to have added strength at the recesses 24 a, since the sidewalls 27 between recesses 24 a may be thicker at the bottom. It will be understood however, that the sidewalls 27 may be formed at various different angles a and shapes within the scope of the present disclosure. The sidewalls may be substantially vertical, and the bottom portions 29 may be substantially horizontal. In other implementations, it will be understood that the sidewalls 27 of the recesses 24 may be formed at a slope and the bottom portions 29 may be configured to be flat, or the sidewalls 27 and bottom portions 29 may both be curved. The spacer 10 may have flat or pointed surfaces at the top of the recesses 24.

Also, the alternative embodiment spacer 11 may have side recesses 25. FIG. 12 shows a cross-sectional view of the alternative embodiment spacer 11, taken along the line A-A in FIG. 11, which shows the side recesses 25 extending within the spacer 11. The side recesses 25 may be configured for receiving positioning means for enabling a surgeon to adjust a position of the spacer 11 when the spacer 11 resides between the adjacent intervertebral bodies 31. The positioning means may be formed as a rod member and may be received in the recesses 25 on both sides of the spacer 11 to facilitate manipulation of the spacer 11.

Some of the primary goals in intervertebral fusion are immobilization of the affected vertebrae, interbody arthrodesis, restoration of the spinal disc space, and sagittal alignment, and to provide an environment for bony fusion between vertebral bodies. Applicants have discovered that these goals may be most effectively accomplished by the mechanical principle of a cantilever. Using the spacer 10 as a compression point, a cantilever may be constructed within the disc space as shown most clearly in FIG. 8D. The procedure for accomplishing this is as follows.

FIG. 8A is a schematic side, internal view of the vertebral bodies 31 indicated in FIG. 5. The spinal disc 33 resides between the vertebral bodies 31, all of which reside between the anterior longitudinal ligament (ALL) 36 and the posterior longitudinal ligament (PLL) 38. The dural nerve (Dura) 40 resides posteriorly to the vertebral bodies 31 and the PLL 38.

Referring now to FIG. 8B and FIG. 9, posterior access to the spine of the patient (not shown) may be accomplished. A right handed surgeon may be positioned on the patient's left side to perform the procedure. Posterior instrumentation, such as pedicle screws 42 (FIG. 9), may be affixed to posterior pedicle portions 34 of the vertebral bodies 31. The associated rods 44 and structure interconnecting the rods 44 with the pedicle screws 42 are not affixed until later on in the procedure. A posterior portion of the lower vertebral body involved in the fusion, namely, the left inferior articular facet or articular process, may be removed and saved for future autogenous bone grafting. A lamina spreader or detractor (not shown, but indicated in FIGS. 8B and 8C), may be placed between the spinous processes 35 (shown in FIG. 5), and may be operated to spread the adjacent vertebral bodies 31 apart. A nerve root retractor (not shown) may be used to protect the dura during the surgery. The anterior longitudinal ligament 36 and posterior longitudinal ligament 38 may be left intact and need not be retracted.

After coagulation of the veins (not shown), the incision 32 (FIG. 5) may be made, with a #15 scalpel, or any suitable surgical instrument, in a side section of the annulus 37. The disc 33 may then be detached from the vertebral end plates (not shown) with the proper surgical instrumentation, and may be removed through the incision 32. Curettes (not shown) and pituitary rongeurs (not shown) may be used to remove the disc material. Care should be taken not to violate the bony vertebral end plate, which would cause excessive bleeding and compromise the resistance to axial load when the spacer 10 is inserted.

When as much disc material has been removed as can safely be accomplished, a trial spacer 50 may be used to determine the correct spacer size. The trial spacer 50 may have the same shape as the spacer 10, both of which are part of a set having various sizes, except that the trial spacer 50 may not include the recesses 24. The trial spacer 50 may be inserted into the incision 32 with a sheathed trocar device 52. The main purpose of trial spacer 50 is to evaluate a snugness of fit of said trial spacer 50 as it resides between the adjacent vertebral bodies 31, which enables the surgeon to determine a spacer size thereby. The trial spacer 50 may also dilate the disc space between the adjacent vertebral bodies 31. The trial spacer 50 may also have sharp edging, and may be used to clear away any remaining unwanted tissue.

When the spacer size has been determined, a bone graft may be prepared using autogenous bone graft material 54 as shown in FIG. 8C. Care is taken to remove all soft tissue from the autogenous bone, which will facilitate successful osteointegration of the graft. Additional bone can also be harvested from the spinous processes 35. Optimally, 6-10 cm³ of morselized bone graft material may be used, but it will be at the discretion of the surgeon to determine how much bone grafting material will be used. The harvested autogenous bone may then be passed through a bone mill (not shown) to form suitable bone grafting material as known and understood to those having ordinary skill in the art.

The spacer 10 may be inserted through the incision 32 with the sheathed trocar device 52. The sheathed trocar device 52 includes a trocar rod 56 that may be slidably disposed within a hollow sheath 58. The trocar rod 56 and the hollow sheath 58 may moveably engaged with each other in any suitable manner.

Both the trial spacer 50 and the spacer 10 may include a female-threaded opening 50 a and 10 a formed therein, respectively, in which a male-threaded portion 57 of the trocar rod 56 may be releasably inserted. The trocar rod 56 may of course be releasably attached to the trial spacer 50 and spacer 10 in any other suitable manner. The trocar rod 56 may have a longer length than the sheath member 58, such that a proximal portion 60 of the trocar rod 56 protrudes from the sheath member 58 when the trocar rod 56 is attached to the trial spacer 50 or the spacer 10.

The sheathed trocar device 52 accordingly may provide an efficiently stabilized, releasable connection with the spacer 10. With the trocar rod 56 being attached directly to the spacer 10, the sheath member 58 may provide additional support by abutting up against the spacer and contactably circumscribing the point of the attachment of the trocar rod 56 with the spacer 10, thereby providing additional stability and control over the positioning of the spacer 10.

The surgeon may then selectively position the spacer 10 within the space residing between the adjacent vertebral bodies 31, as far anteriorly as possible such that the spacer 10 may reside in contact with the anterior longitudinal ligament 36. Proper placement of the spacer 10 can be checked with the use of X-rays.

With the spacer 10 in place, the bone grafting material 54 may be placed through the incision 32 and into position between the adjacent vertebral bodies 31, such that said bone grafting material 54 resides posteriorly to the concave sidewall 14 of the spacer 10, and thus between the sidewall 14 and the posterior longitudinal ligament 38. A bone funnel (not shown) as known to those having ordinary skill in the field may be used to funnel morselized bone grafting material into the incision 32. A bone tamp (not shown) may be used by the surgeon to tamp the bone grafting material against the spacer 10.

It is noted that the concavo-convex shape of the spacer 10, and the method of implantation with the spacer 10 residing as far anteriorly as possible, operates to provide a larger bone-graft interface between the adjacent vertebral bodies 31.

Referring now to FIG. 8D and FIG. 9, the lamina spreader may be removed and the pedicle screws 42 may be interconnected with the rods 44 as known in the field. Mild compression may be applied by a compression instrument 46 to thereby slide rods 44 downwardly, after which the pedicle screws 42 may be tightened to hold the rods 44 in place and maintain the compression. Further compression may be applied as desired, with the result being illustrated schematically in FIG. 8D. The bone grafting material 54 may thereby be loaded in compression by the posteriorly compressed adjacent vertebral bodies 31 as shown. After final inspection of the placement of the bone grafting material 54, routine closure of the wound may be completed. The use of drains may be made at the discretion of the surgeon.

The spacer 10 may thus operate to cause the adjacent vertebral bodies 31 to be suspended in the manner of a cantilever. The posterior compression provided by the pedicle screws 42 and rods 44, which may alternatively be provided by any other suitable holding structure, causes the adjacent vertebral bodies 31 to be brought closer together on their posterior side than on their anterior side, consistent with the natural sagittal alignment in which they were originally positioned, as understood by those having ordinary skill in the field.

It will be appreciated that the structure and apparatus of the trocar rod 56 and sheath 58 constitute a positioning means for enabling a surgeon to adjust a position of the spacer 10 when the spacer 10 resides between the adjacent intervertebral bodies 31. That structure is merely one example of a means for positioning the spacer 10, and it should be appreciated that any structure, apparatus or system for positioning which performs functions that are the same as, or equivalent to, those disclosed herein are intended to fall within the scope of a means for positioning, including those structures, apparatus or systems for positioning which are presently known, or which may become available in the future. Anything which functions the same as, or equivalently to, a means for positioning falls within the scope of this element.

In accordance with the features and combinations described above, a useful method of implanting an artificial intervertebral disc includes:

(a) making an incision in an annulus of a human spinal column between adjacent vertebral bodies of said spinal column to thereby expose a space residing between said adjacent vertebral bodies;

(b) removing the disc material from between said adjacent vertebral bodies, being careful not to injure the disc plates;

(c) inserting a spacing member and autogenous bone grafting material through the incision and into position between the adjacent vertebral bodies, and positioning said spacing member at an anterior location with respect to the spinal column such that more intervertebral space resides posteriorly to said spacing member than anteriorly thereto; and

(d) applying compression to posterior portions of the adjacent vertebral bodies.

Those having ordinary skill in the relevant art will appreciate the advantages provided by the features of the present disclosure. For example, it is a feature of the present disclosure to provide an intervertebral spacing system that does not require an additional, anterior surgical procedure. It is another feature of the present disclosure, in accordance with one aspect thereof, to provide such an intervertebral spacing system by which sagittal alignment of the spine may be restored. It is a further feature of the present disclosure, in accordance with one aspect thereof, to provide such an intervertebral spacing system that can accommodate a larger host-graft interface between adjacent vertebral bodies. It is an additional feature of the present disclosure, in accordance with one aspect thereof, to provide such an intervertebral spacing system in which bone grafting material may be loaded in compression between adjacent vertebral bodies of the spine. It is yet another feature of the present disclosure, in accordance with one aspect thereof, to provide such an intervertebral spacing system that does not require retraction of the dural nerve, or of the anterior or posterior longitudinal ligaments, for implantation of the spacer.

It is to be understood that the above-described arrangements are only illustrative of the application of the principles of the present disclosure. Numerous modifications and alternative arrangements may be devised by those skilled in the art without departing from the spirit and scope of the present disclosure and the appended claims are intended to cover such modifications and arrangements. Thus, while the present disclosure has been shown in the drawings and described above with particularity and detail, it will be apparent to those of ordinary skill in the art that numerous modifications, including, but not limited to, variations in size, materials, shape, form, function and manner of operation, assembly and use may be made without departing from the principles and concepts set forth herein. 

1. An intervertebral spacing implant comprising: a spacing member adapted for implanting between adjacent vertebral bodies of a human spine as a load-bearing replacement for a spinal disc, said spacing member further comprising an external, concavo-convex contour with respect to one dimension of said spacing member; wherein the spacing member comprises a solid body; wherein the spacing member comprises an upper surface and a lower surface and a free insertion end, and wherein at least one of said upper surface and said lower surface comprises a male corner line, and wherein said spacing member includes a tapered portion between said male corner line and said free insertion end of said spacing member such that said spacing member becomes progressively thinner from said male corner line toward said free insertion end of said spacing member, wherein said tapered portion is characterized by at least one smooth surface that is a part of either said upper surface or said lower surface and extends from said male corner line to said free insertion end, said smooth surface having an absence of corners, points or other abrupt edges; and wherein said spacing member comprises a sidewall around a perimeter of said spacing member, said sidewall having a smooth contour characterized by an absence of corners extending from said upper surface to said lower surface.
 2. The intervertebral spacing implant of claim 1, wherein the spacing member is either inherently non-porous or is otherwise rendered non-porous.
 3. The intervertebral spacing implant of claim 1, wherein the spacing member is constructed from a rigid, non-resilient load-bearing material.
 4. The intervertebral spacing implant of claim 1, wherein the spacing member defines an imaginary arcuate centerline residing between opposing sides of the external concavo-convex contour of said spacing member, said arcuate centerline forming less than half a circle.
 5. The intervertebral spacing implant of claim 1, wherein said spacing member has a cashew shape having a uniform width along a majority length of the spacing member.
 6. The intervertebral spacing implant of claim 1, wherein the spacing member comprises a bone material.
 7. The intervertebral spacing implant of claim 1, wherein the spacing member comprises metal.
 8. The intervertebral spacing implant of claim 1, wherein the spacing member comprises titanium.
 9. The intervertebral spacing implant of claim 1, wherein the spacing member comprises ceramic.
 10. The intervertebral spacing implant of claim 1, wherein the spacing member includes an anterior wall and a posterior wall, and wherein the external concavo-convex contour of the spacer is defined by the posterior wall being concave in a horizontal dimension and by the anterior wall being convex in a horizontal dimension.
 11. The intervertebral spacing implant of claim 10, wherein the anterior wall and the posterior wall of the spacing member are each linear in a vertical dimension.
 12. The intervertebral spacing implant of claim 1, wherein the concavo-convex contour comprises a concave posterior side, and a convex anterior side disposed in a substantially parallel orientation with respect to the concave posterior side.
 13. The intervertebral spacing implant of claim 1, wherein the spacing member further comprises a disc-like member having a thickness at a thickest part of the spacing member, and a length that is greater in length than said thickness at said thickest part, and a width that is greater in width than said thickness at said thickest part.
 14. The intervertebral spacing implant of claim 13, wherein the width of the spacing member is defined by a perimeter wall that constitutes the concave side and the convex side of the external concavo-convex contour of said spacing member.
 15. The intervertebral spacing implant of claim 1, wherein the spacing member further comprises a plurality of spaced-apart recesses formed in said upper surface.
 16. The intervertebral spacing implant of claim 15, wherein the recesses are elongate and are disposed in a substantially parallel orientation with respect to each other.
 17. The intervertebral spacing implant of claim 16, wherein the recesses extend in an anterior-to-posterior direction.
 18. The intervertebral spacing implant of claim 15, wherein the spaced-apart recesses comprise opposing sidewalls disposed at a non-parallel angle with respect to each other.
 19. The intervertebral spacing implant of claim 18, wherein said angle is within a range of between approximately 45 degrees and 75 degrees.
 20. The intervertebral spacing implant of claim 19, wherein said angle is approximately 60 degrees.
 21. The intervertebral spacing implant of claim 1, wherein said spacing member further comprises attachment means for releasably attaching positioning means to said spacing member.
 22. The intervertebral spacing implant of claim 21, wherein said attachment means are positioned on an end of said spacing member opposite said free insertion end.
 23. The intervertebral spacing implant of claim 21, wherein said attachment means for releasably attaching positioning means to said spacing member comprises a recess in said spacing member.
 24. The intervertebral spacing implant of claim 23, wherein said attachment means for releasably attaching positioning means to said spacing member comprises a threaded bore.
 25. An intervertebral spacing implant comprising: a spacing member adapted for implanting between adjacent vertebral bodies of a human spine as a load-bearing replacement for a spinal disc, said spacing member further comprising an external, concavo-convex contour with respect to one dimension of said spacing member; wherein the spacing member defines an imaginary arcuate centerline residing between opposing sides of the external concavo-convex contour of said spacing member; wherein the spacing member comprises a first end, a second end, and a length between said first end and said second end; wherein said spacing member includes a tapered portion at said second end such that said spacing member becomes progressively thinner toward said second end of said spacing member; wherein said tapered portion extends along only a portion of said length; and wherein said spacing member comprises a sidewall around a perimeter of said spacing member, said sidewall having a smooth contour characterized by an absence of corners extending from said upper surface to said lower surface.
 26. The intervertebral spacing implant of claim 25, wherein the spacing member is solid and is either inherently non-porous or is otherwise rendered non-porous.
 27. The intervertebral spacing implant of claim 25, wherein the spacing member is constructed from a rigid, non-resilient load-bearing material.
 28. The intervertebral spacing implant of claim 25, wherein said arcuate centerline forms less than half a circle.
 29. The intervertebral spacing implant of claim 25, wherein said spacing member has a cashew shape having a uniform width along a majority length of the spacing member.
 30. The intervertebral spacing implant of claim 25, wherein the spacing member comprises a bone material.
 31. The intervertebral spacing implant of claim 25, wherein the spacing member includes an anterior wall and a posterior wall, and wherein the external concavo-convex contour of the spacer is defined by the posterior wall being concave in a horizontal dimension and by the anterior wall being convex in a horizontal dimension.
 32. The intervertebral spacing implant of claim 31, wherein the anterior wall and the posterior wall of the spacing member are each linear in a vertical dimension.
 33. The intervertebral spacing implant of claim 25, wherein the concavo-convex contour comprises a concave posterior side, and a convex anterior side disposed in a substantially parallel orientation with respect to the concave posterior side.
 34. The intervertebral spacing implant of claim 25, wherein the spacing member further comprises a disc-like member having a thickness at a thickest part of the spacing member, and a length that is greater in length than said thickness at said thickest part, and a width that is greater in width than said thickness at said thickest part.
 35. The intervertebral spacing implant of claim 34, wherein the width of the spacing member is defined by a perimeter wall that constitutes the concave side and the convex side of the external concavo-convex contour of said spacing member.
 36. The intervertebral spacing implant of claim 25, wherein the spacing member further comprises a plurality of spaced-apart recesses formed in said upper surface.
 37. The intervertebral spacing implant of claim 36, wherein the recesses are elongate and are disposed in a substantially parallel orientation with respect to each other.
 38. The intervertebral spacing implant of claim 37, wherein the recesses extend in an anterior-to-posterior direction.
 39. The intervertebral spacing implant of claim 36, wherein the spaced-apart recesses comprise opposing sidewalls disposed at a non-parallel angle with respect to each other.
 40. The intervertebral spacing implant of claim 39, wherein said angle is within a range of between approximately 45 degrees and 75 degrees.
 41. The intervertebral spacing implant of claim 40, wherein said angle is approximately 60 degrees.
 42. The intervertebral spacing implant of claim 25, wherein said spacing member further comprises attachment means for releasably attaching positioning means to said spacing member.
 43. The intervertebral spacing implant of claim 42, wherein said attachment means are positioned on an end of said spacing member opposite said free insertion end.
 44. The intervertebral spacing implant of claim 42,. wherein said attachment means for releasably attaching positioning means to said spacing member comprises a recess in said spacing member.
 45. The intervertebral spacing implant of claim 42, wherein said attachment means for releasably attaching positioning means to said spacing member comprises a threaded bore.
 46. An intervertebral spacing implant comprising: a spacing member adapted for implanting between adjacent vertebral bodies of a human spine as a load-bearing replacement for a spinal disc, said spacing member further comprising an external, concavo-convex contour with respect to one dimension of said spacing member; wherein the spacing member defines an imaginary arcuate centerline residing between opposing sides of the external concavo-convex contour of said spacing member, said arcuate centerline forming less than half a circle, said spacing member further comprising an upper surface, a lower surface, and a sidewall extending around a perimeter of said spacing member between said upper surface and said lower surface, and wherein said sidewall has a smooth contour characterized by an absence of corners extending from said upper surface to said lower surface; wherein the spacing member comprises a bone material.
 47. The intervertebral spacing implant of claim 46, wherein the spacing member is solid and is either inherently non-porous or is otherwise rendered non-porous.
 48. The intervertebral spacing implant of claim 46, wherein the spacing member is constructed from a rigid, non-resilient load-bearing material.
 49. The intervertebral spacing implant of claim 46, wherein the spacing member comprises a first end, a second end, and a length between said first end and said second end; wherein said spacing member includes a tapered portion at said second end such that said spacing member becomes progressively thinner toward said second end of said spacing member; wherein said tapered portion extends along a portion of said length such that said tapered portion covers less than approximately 25% of said length.
 50. The intervertebral spacing implant of claim 46, wherein said spacing member has a cashew shape having a uniform width along a majority length of the spacing member.
 51. The intervertebral spacing implant of claim 46, wherein the spacing member includes an anterior wall and a posterior wall, and wherein the external concavo-convex contour of the spacer is defined by the posterior wall being concave in a horizontal dimension and by the anterior wall being convex in a horizontal dimension.
 52. The intervertebral spacing implant of claim 51, wherein the anterior wall and the posterior wall of the spacing member are each linear in a vertical dimension.
 53. The intervertebral spacing implant of claim 46, wherein the concavo-convex contour comprises a concave posterior side, and a convex anterior side disposed in a substantially parallel orientation with respect to the concave posterior side.
 54. The intervertebral spacing implant of claim 46, wherein the spacing member further comprises a disc-like member having a thickness at a thickest part of the spacing member, and a length that is greater in length than said thickness at said thickest part, and a width that is greater in width than said thickness at said thickest part.
 55. The intervertebral spacing implant of claim 54, wherein the width of the spacing member is defined by a perimeter wall that constitutes the concave side and the convex side of the external concavo-convex contour of said spacing member.
 56. The intervertebral spacing implant of claim 46, wherein the spacing member further comprises a plurality of spaced-apart recesses formed in said upper surface.
 57. The intervertebral spacing implant of claim 36, wherein the recesses are elongate and are disposed in a substantially parallel orientation with respect to each other.
 58. The intervertebral spacing implant of claim 57, wherein the recesses extend in an anterior-to-posterior direction.
 59. The intervertebral spacing implant of claim 56, wherein the spaced-apart recesses comprise opposing sidewalls disposed at a non-parallel angle with respect to each other.
 60. The intervertebral spacing implant of claim 59, wherein said angle is within a range of between approximately 45 degrees and 75 degrees.
 61. The intervertebral spacing implant of claim 60, wherein said angle is approximately 60 degrees.
 62. The intervertebral spacing implant of claim 46, wherein said spacing member further comprises attachment means for releasably attaching positioning means to said spacing member.
 63. The intervertebral spacing implant of claim 62, wherein said attachment means are positioned on an end of said spacing member opposite a free insertion end.
 64. The intervertebral spacing implant of claim 62, wherein said attachment means for releasably attaching positioning means to said spacing member comprises a recess in said spacing member.
 65. The intervertebral spacing implant of claim 62, wherein said attachment means for releasably attaching positioning means to said spacing member comprises a threaded bore.
 66. A method of implanting an artificial intervertebral disc comprising: (a) making an incision in an annulus of a human spinal column between adjacent vertebral bodies of said spinal column to thereby expose a space residing between said adjacent vertebral bodies; (b) inserting a trial spacer through the incision and into position between the adjacent vertebral bodies, and evaluating a snugness of fit of said spacer as it resides between said adjacent vertebral bodies and determining a spacer size thereby; and (c) inserting a spacing member, with a tapered end of said spacing member first, through the incision and into position between the adjacent vertebral bodies, and positioning said spacing member at an anterior location with respect to the spinal column such that more intervertebral space resides posteriorly to said spacing member than anteriorly thereto.
 67. The method of claim 66, wherein part (b) further comprises dislodging any unwanted soft tissue from between the vertebral bodies with the trial spacer.
 68. The method of claim 66, further comprising inserting said trial spacer through the incision in an arcuate path.
 69. The method of claim 66, further comprising applying compression to posterior portions of the adjacent vertebral bodies.
 70. A method of implanting an artificial intervertebral disc comprising: (a) making an incision in an annulus of a human spinal column between adjacent vertebral bodies of said spinal column to thereby expose a space residing between said adjacent vertebral bodies; (b) selecting a spacing member comprising an external concavo-convex contour with respect to one dimension of said spacing member, wherein said spacing member comprises a solid body, wherein said spacing member comprises an upper surface, a lower surface and a free insertion end, and wherein said spacing member includes a tapered portion such that said spacing member becomes progressively thinner toward said free insertion end of said spacing member; and (c) inserting said spacing member, with said tapered portion of said spacing member first, through the incision and into position between the adjacent vertebral bodies, and positioning said spacing member at an anterior location with respect to the spinal column such that more intervertebral space resides posteriorly to said spacing member than anteriorly thereto.
 71. The method of claim 70, further comprising applying compression to posterior portions of the adjacent vertebral bodies.
 72. The method of claim 70, further comprising removing a natural human disc from the space.
 73. The method of claim 70, further comprising attaching an insertion instrument to said spacing member.
 74. The method of claim 73, wherein attaching an insertion instrument to said spacing member comprises threading a trocar on said spacing member.
 75. The method of claim 71, further comprising compressing the posterior portions of the adjacent vertebral bodies toward each other to a degree sufficient to move said adjacent vertebral bodies into a sagittal alignment.
 76. The method of claim 75, further comprising attaching a holding means to the adjacent vertebral bodies for holding said adjacent vertebral bodies in the sagittal alignment to thereby inhibit said vertebral bodies from moving out of sagittal alignment.
 77. The method of claim 76, wherein attaching holding means further comprises affixing pedicle screws to posterior pedicle portions of the vertebral bodies, and interconnecting rods with the pedicle screws.
 78. The method of claim 70, further comprising removing a posterior portion of one of the vertebral bodies for autogenous bone grafting.
 79. The method of claim 70, further comprising placing a lamina spreader between spinous processes to spread adjacent vertebral bodies apart.
 80. The method of claim 70, further comprising preparing a bone graft from autogenous bone graft material.
 81. The method of claim 80, further comprising harvesting autogenous bone and passing said autogenous bone through a mill to form said autogenous bone graft material.
 82. The method of claim 70, further comprising bringing the adjacent vertebral bodies closer together on a posterior side than on an anterior side. 